The present invention relates to a dehydrating agent for use in the processing of histological or cytological samples and more particularly relates to a novel combination of alcohols as fixative/dehydrating agents in the processing of histological or cytological samples.
The processing of tissue samples for pathological diagnosis requires a high quality conditioning of the tissue samples for attachment to glass slides which will be reviewed in the pathological diagnosis. In the processing of tissues for glass slides, the tissues are clinically removed from a patient and placed in a container which often contains a fixative and is then transported to the lab for further treatment or conditioning. The chemical reagents used as fixatives are those which will preserve the tissue components in a life-like manner. The tissue received in the fixative filled container are then generally cut into small sections, usually from 3 to 5 mms in thickness, and placed into vented, plastic cassettes. These cassettes are then placed into a tissue processor where they are subjected to a series of chemical reagents wherein the tissue, after being fixed, will be dehydrated, cleared and infiltrated generally with paraffin. The dehydrating step involves the removal of aqueous and some of the liquid tissue fluids with dehydrating agents. The clearing step involves the use of selected fluids to remove the dehydrating agent. In the infiltration with paraffin, the infiltration medium provides cellular support thereby enabling easy cutting of the tissue into sections for placement upon a slide, enabling pathologists the best possible specimen for diagnosing.
In the dehydrating step in the processing of tissue specimens, ethyl alcohol has been for many years the predominate liquid dehydrating agent. Moreover, ethyl alcohol has found use as a cytology fixative. In recent years, isopropyl alcohol and methyl alcohol have been suggested as alternatives to ethyl alcohol, but each of these alcohols used alone have proven to be unsatisfactory. However, U.S. Pat. No. 4,911,915 which issued to Fredenburgh on Mar. 27, 1990 teaches that a mixture of isopropyl alcohol and methyl alcohol in very specific ranges are equal to ethyl alcohol as a fixative and dehydrating agent in tissue specimen conditioning. Specifically, Fredenburgh teaches that a dehydrating agent consisting of from 30% to 45% by volume of methanol and 70 to 55% by volume of isopropyl alcohol works as well as ethyl alcohol in the processing of histological or cytological samples.